Note: Descriptions are shown in the official language in which they were submitted.
CA 02471196 2004-06-11
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VISCOSITY INDEX IMPROVER CONCENTRATES
FIELD OF THE INVENTION
The invention is directed to viscosity index improver concentrates useful in
the
formulation of lubricating ail compositions. More specifically, the present
invention is
directed to viscosity index improver concentrate containing at least one
polymeric viscosity
index improver, and optionally a polymeric lubricating oil flow improver, in
diluent oil,
wherein the diluent oil has specified kinematic viscosity and CCS
characteristics.
BACKGROUND OF THE INVENTION
Lubricating oil compositions for use in crankcase engine oils comprise a major
amount of base stock oil and minor amounts of additives that improve the
performance and
increase the useful Life of the lubricant. Crankcase lubricating oil
compositions
conventionally contain polymeric components that are used to improve the
viscometric
performance of the engine oil, i.e., to provide multigrade oils such as SAE SW-
30, lOW-30
and lOW-40. These viscosity performance enhancers, commonly referred to as
viscosity
index (VI) improvers, include olefin copolymers, polymethacrylates,
styrene/hydrogenated
dime block and star copolymers and hydrogenated isoprene linear and star
polymers.
Olefin copolymers (or OCP) used as VI improvers conventionally comprise
copolymers of ethylene, propylene and, optionally, a diene. High ethylene
content OCP VI
improvers are known to provide reduced lubricating oil resistance to cold
engine starting (as
measured by "CCS" performance). However, polymer chains having long ethylene
sequences
have a more crystalline polymer structure. Crystalline polymers have been
found, primarily
at low temperatures, to interact with waxes in the oil and other OCP chains,
which results in
uncontrollable increases in low temperature viscosity and, in extreme cases,
the gelling of the
lubricating oil. These problems have been found to manifest in Ziegler Natta
polymerized
OCPs containing greater than about 60 mass % polymer derived from ethylene
(hereinafter
referred to as "high ethylene content", or "crystalline" OCP(s)").
VI improvers are commonly provided to lubricating oil blenders as a
concentrate in
which the VI improver polymer is diluted in oil to allow, inter alia, for more
facile
dissolution of the VI irnprover in the base stock oil. A typical VI improver
concentrate can
contain as little as 4 mass % active polymer, with the remainder being diluent
oil. A typical
formulated multigrade crankcase lubricating oil may, depending on the
thickening efficiency
(TE) of the polymer, require as much as 3 mass % of active VI irnprover
polymer. An
CA 02471196 2004-06-11
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additive concentrate providing this amount of polymer can introduce as much as
15 mass %,
based on the total mass of the finished lubricant, of diluent oil.
There has been a continued demand for lubricating oil compositions providing
improved fuel economy. There has also been a continuous demand for VI
improvers that
provide improved CCS performance in formulated lubricating oil compositions,
without wax
and polymer chain interaction (gelling). Much effort has been made in these
respects to select
the proper base stock oil and to provide a low ethylene content (amorphous) VI
improver
having improved CCS performance. However, little attention has been paid to
the selection
of the diluent oil used to form the VI improver concentrate. As the additive
industry is highly
competitive from a pricing standpoint, and diluent oil represents one of the
largest raw
material costs to the additive manufacturers, VI improver concentrates have
commonly
contained the least expensive oil capable of providing suitable handling
characteristics;
usually a solvent neutral (SN) 100 or SN150 Group 1 oil. Using such
conventional VI
improver concentrates, the finished lubricant formulator has needed to add a
quantity of
relatively high quality base stock oil, as a correction fluid, to insure the
formulation CCS
remained within specification.
As lubricating oil performance standards have become more stringent, there has
been
a continuing need to identify components capable of conveniently and cost
effectively
improving overall lubricant performance. Therefore, it would be advantageous
to be able to
provide a VI improver concentrate that delivers improved cold temperature
performance,
regardless of the VI improver employed, without requiring use of correction
fluids.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, there is provided a
viscosity index
(VI) improver concentrate comprising at least one polymeric VI improving
material,
optionally a polymeric lubricating oil flow improver (LOFI) material, and
diluent oil, wherein
the diluent oil has a kinematic viscosity at 100°C (kvi~) of at least
3.0 and CCS at -35°C of
less than 3700 cPs, and wherein at least 98 mass % of said concentrate
consists essentially of
VI improving material, LOFI material and diluent oil.
In accordance with a second aspect of the invention, there is provided a (VI)
improver
concentrate, as in the first aspect, wherein the diluent oil has a~ Noack
volatility of less than 40
mass %.
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In accordance with a third aspect of the invention, there is provided a VI
improver
concentrate, as in the first or second aspect, wherein the concentrate has a
kinematic viscosity
at 100°C (kvl~) of from about 300 to about 2500 cSt.
In accordance with a fourth aspect of the invention, there is provided a VI
improver
concentrate, as in the first, second or third aspect, wherein the VI improver
is a copolymer of
ethylene and another a-olefin (OCP).
In accordance with a fifth aspect of the invention, there is provided a VI
improver
concentrate, as in the fourth aspect, wherein the VI improver is an amorphous
OCP.
Other and further objects, advantages and features of the present invention
will be
understood by reference to the following specification.
DETAILED DESCRIPTION OF THE INVENTION
VI improvers useful in the practice of the invention include ethylene-p,-
olefin
copolymers (OCP) synthesized from ethylene monomer and at least one other a-
olefin
comonomer. The average ethylene content of OCP useful in the present invention
can be as
low as about 20% on a mass basis; preferably about 25%; mare preferably about
30%. The
maximum ethylene content can be about 90% on a mass basis; preferably about
85%; most
preferably about 80%. OCP intended for use as viscosity modifiers typically
comprise from
about 35 to 75 wt. % ethylene but more preferably are "amorphous" or
substantially
amorphous copolymers comprising less than about 60 mass %, (e.g. 40 to 56 mass
%)
ethylene. Crystalline ethylene-a-olefin copolymers are defined as those
comprising greater
than about 60 mass ethylene (e.g. from about 60 to about 90 mass % ethylene).
Conversely,
amorphous or substantially amorphous ethylene-a-olefin copolymers used as VI
improving
materials typically comprise from about 25 to about 60 mass % ethylene;
preferably from
about 30 to about 60 mass % ethylene; more preferably from about 35 to about
60 mass %
ethylene. Ethylene content can be measured by ASTM-D3900 for ethylene-
propylene
copolymers containing between 35 mass % and 85 mass % ethylene. Above 85 mass
%,
ASTM-D2238 can be used to obtain methyl group cancentratian, which is related
to percent
ethylene in an unambiguous manner for ethylene-propylene copolymers. When
comonomers
other than propylene are employed, no ASTM tests covering a wide range of
ethylene
contents are available; however, proton and carbon-13 nuclear magnetic
resonance
spectroscopy can be employed to determine the composition of such polymers.
These are
CA 02471196 2004-06-11
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absolute techniques requiring no calibration when operated. such that all
nuclei of a given
element contribute equally to the spectra. For ethylene content ranges not
covered by the
ASTM tests for ethylene-propylene copolymers, as well as for any ethylene-
propylene
copolymers, the aforementioned nuclear magnetic resonance methods can also be
used.
As noted, the ethylene-a,-olefin copolymers are comprised of ethylene and at
least one
other a-olefin. The "other" a-olefins typically include those containing 3 to
18 carbon atoms,
e.g., propylene, butene-1, pentene-1, etc. Preferred are a-olefins having 3 to
6 carbon atoms,
particularly for economic reasons. The most preferred OCP are those comprised
of ethylene
and propylene.
As is well known to those skilled in the art, copolymers of ethylene and
higher alpha-
olefins such as propylene can optionally include other polyrnerizable
monomers. Typical of
these other monomers are non-conjugated dienes such as the following non-
limiting
examples:
a. straight chain acyclic dimes such as: 1,4-hexadiene; 1,6-octadiene;
b. branched chain acyclic dimes such as: 5-methyl-l, 4-hexadiene; 3, 7-
dimethyl-1,6-
octadiene; 3, 7-dimethyl-1,7-octadiene and the mixed isomers of dihydro-mycene
and
dihydroocinene;
c. single ring alicyclic dimes such as: 1, 4-eyclohexadiene; 1,5-
eyclooctadiene; and 1,5-
cyclododecadiene; and
d. multi-ring alicyclic fused and bridged ring dimes such as:
tetrahydroindene;
methyltetrahydroindene; dicyclopentadiene; bicyclo-(2,2,1)-hepta-2, 5-dime;
alkenyl,
alkylidene, cycloalkenyl and cycloalkylidene norbornenes such as 5-methylene-2-
norbornene (MNB), 5-ethylidene-2-norbornene (ENB), 5-propylene-2-norbornene, 5-
isopropylidene-2-norbornene, 5-(4-eyclopentenyl)-2-norbornene; 5-
cyclohexylidene-2-
norbornene.
Of the non-conjugated dimes typically used to prepare these copolymers, dimes
containing at least one of the double bonds in a strained ring are preferred.
The most
preferred dime is 5-ethylidene-2-norbornene (ENB). Vfher prcsert, tl~e ar ount
of di~:ne (c~,
a weight basis) in the copolymer can be from greater than 0% to about 20%;
preferably from
greater than 0% to about 15%; most preferably greater than 0% to abaut 10%.
The molecular weight of OCP useful in accordance with the present invention
can
vary over a wide range since ethylene copolymers having number-average
molecular weights
(M") as low as about 2,000 can affect the viscosity properties of an
oleaginous composition.
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The preferred minimum M" is about 10,000; the most preferred minimum is about
20,000.
The maximum Mn can be as high as about 12,000,000; the preferred maximum is
about
1,000,000; the most preferred maximum is about 750,000. An especially
preferred range of
number-average molecular weight for OCP useful in the present invention is
from about
15,000 to about 500,000; preferably from about 20,000 to about 250,000; more
preferably
from about 25,000 to about 150,000. The term "number average molecular
weight", as used
herein, refers to the number average weight as measured by Gel Permeation
Chromatography
("GPC") with a polystyrene standard.
Other VI improvers useful in the practice of the invention include
homopolymers and
copolymers of diolefins containing from 4 to about 12 carbon atoms, preferably
from 8 to
about 16 carbon atoms, such as 1,3-butadiene, isoprene, piperylene,
methylpentadiene,
phenylbutadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadiene, and
copolymers of
one or more conjugated diolefins and one or more monoalkenyl aromatic
hydrocarbons
containing from 8 to about 16 carbon atoms such as aryl-substituted styrenes,
alkoxy-
substituted styrenes, vinyl naphthalene, alkyl-substituted vinyl naphthalenes
and the like.
Such polymers and copolymers include random polymers, tapered polymers and
block
copolymers and may be of a star or linear structure.
Linear block copolymers useful in the practice of the present invention may be
represented by the following general formula:
AZ_(B _A)r-B X
wherein:
A is a polymeric block comprising predominantly monoalkenyl aromatic
hydrocarbon
monomer units;
B is a polymeric block comprising predominantly conjugated diolefin monomer
units;
x and z are, independently, a number equal to 0 or l; and
y is a whole number ranging from 1 to about 15.
Useful tapered linear block copolymers may be represented by the following
general
formula:
A-A/B-B
wherein:
CA 02471196 2004-06-11
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A is a polymeric block comprising predominantly monoalkenyl aromatic
hydrocarbon
monomer units;
B is a polymeric block comprising predominantly conjugated diolefin monomer
units;
and
A/B is a tapered segment containing both monoalkenyl aromatic hydrocarbon and
conjugated diolefin units.
Radial or star polymers may be represented, generally, by the following
general
formula:
(BX (A-B)Y-Az)"C; and
(B' x (A-B)y-Az)n'-C(B' )n"
wherein:
A, B, x, y and z are as previously defined;
n is a number from 3 to 30;
C is the core of the radial polymer formed with a polyfunctional coupling
agent;
B' is a polymeric block comprising predominantly conjugated diolefm units,
which
B' may be the same or different from B; and
n' and n" are integers representing the number of each type of arm and the sum
of n'
and n" will be a number from 3 to 30.
As used herein in connection with polymer block composition, predominantly
means
that the specified monomer or monomer type which is the principle component in
that
polymer block is present in an amount of at least 85% by weight of the block.
Polymers prepared with diolefms will contain ethylenic unsaturation, and such
polymers are preferably hydrogenated. When the polymer is hydrogenated, the
hydrogenation may be accomplished using any of the techniques known in the
prior art. For
example, the hydrogenation may be accomplished such that both ethylenic and
arorxia.tic
unsaturation is converted (saturated) using methods such as those taught, for
example, in U.S.
Pat. Nos. 3,113,986 and 3,700,633 or the hydrogenation may be accomplished
selectively
such that a significant portion of the ethylenic unsaturation is converted
while little or no
aromatic unsaturation is converted as taught, for example, in U.S. Pat. Nos.
3,634,595;
3,670,054; 3,700,633 and Re 27,145. Any of these methods can also be used to
hydrogenate
polymers containing only ethylenic unsaturation and which are free of aromatic
unsaturation.
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Polymeric VI impravers may include mixtures of linear polymers as disclosed
above,
but having different molecular weights and/or different alkenyl aromatic
contents as well as
mixtures of star polymers having different molecular weights andlor different
alkenyl
aromatic contents. Alternatively, mixtures of star polymers and linear
polymers having
different molecular weights and/or different alkenyl aromatic contents may be
used. The use
of two or more different polymers may be preferred to a single polymer
depending on the
rheological properties the product is intended to impart when used to produce
formulated
engine oil. Mixtures of, for example, OCP and star polymers are also known.
In general, number average molecular weights of between about 200,000 and
about
1,500,000 are acceptable, and between about 350,000 and about 900,000 are
preferred, and
between about 350,000 and about 800,000 are most preferred far the base
polymer when the
base polymer is a star-configuration hydrogenated polymer of one or more
conjugated olefins
or a star configuration polymer of one or more alpha olefins. When the base
polymer is a star
configuration copolymer containing more than about 3% by weight of monoalkenyl
arenes,
the number average molecular weight is preferably between about 350,000 and
about 800,000.
When the base polymer is a copolymer of monoalkenyl arene and polymerized
alpha
olefins, hydrogenated polymerized diolefins or combinations thereof, the
amount of
monoalkenyl arene in the base palymer is preferably between about 5% and about
40% by
weight of the base polymer. For such polymers, number average molecular
weights between
about 85,000 and about 300,000 are acceptable.
Useful copolymers of this type include those prepared in bulk, suspension,
solution or
emulsion. As is well known, polymerization of monomers to produce hydrocarbon
polymers
may be accomplished using free-radical, cationic and anionic initiators or
polymerization
catalysts, such as transition metal catalysts used for Ziegler-Natta and
metallocene type
catalysts.
Optionally, the VI improvers used in the practice of the invention can be
provided
with nitrogen-containing functional groups that impart dispersant capabilities
to the VI
improver. One trend in the industry has been tv use such "multifunctional" VI
improvers in
lubricants to replace some or all of the dispersant. Nitrogen-containing
functional groups can
be added to a polymeric VI improver by grafting a nitrogen- or hydroxyl-
containing moiety,
preferably a nitrogen-containing moiety, onto the polymeric backbone of the VI
improver
CA 02471196 2004-06-11
- g
(functionalizing). Processes for the grafting of a nitrogen-containing moiety
onto a polymer
are known in the art and include, for example, contacting the polymer and
nitrogen-containing
moiety in the presence of a free radical initiator, either neat, or in the
presence of a solvent.
The free radical initiator may be generated by shearing (as in an extruder) or
heating a free
radical initiator precursor, such as hydrogen peroxide.
The amount of nitrogen-containing grafting monomer will depend, to some
extent, on
the nature of the substrate polymer and the level of dispersancy required of
the grafted
polymer. To impart dispersancy characteristics to both star and linear
copolymers, the
amount of grafted nitrogen-containing monomer is suitably between about 0.4
and about 2.2
wt. %, preferably from about 0.5 to about 1.8 wt. %, most preferably from
about 0.6 to about
1.2 wt. %, based on the total weight of grafted polymer.
Methods for grafting nitrogen-containing monomer onto polymer backbones, and
suitable nitrogen-containing grafting monomers are known and described, for
example, in U.S.
Patent No. 5,141,996, WO 98/13443, WO 99121902, U.S. Patent No. 4,146,489,
U.S. Patent
No. 4,292,414, and U.S. Patent No. 4,506,056. (See also J Polymer Science,
Part A: Polymer
Chemistry, Vol. 26, 1189-1198 (1988); J. Polymer Science, Polymer Letters,
Vol. 20, 481-
486 (1982) and J. Polymer Science, Polymer Letters, Vol. 21, 23-30 (1983), all
to Gaylord
and Mehta and Degradation and Cross-linkin og f Ethylene-Propylene Copolymer
Rubber on
Reaction with Malefic Anhydride andlor Peroxides; J. Applien Polymer Science,
Vol. 33,
2549-2558 (1987) to Gaylord, Mehta and Mehta.
Oils of lubricating viscosity useful as the diluents of the present invention
may be
selected from natural lubricating oils, synthetic lubricating oils and
mixtures thereof.
Natural oils include animal oils and vegetable oils (e.g., castor oil, lard
oil); liquid
petroleum oils and hydro-refined, solvent-treated or acid-treated mineral oils
of the paraffinic,
naphthenic and mixed paraffinic-naphthenic types. Oils of lubricating
viscosity derived from
coal or shale also serve as useful base oils.
Synthetic lubricating ails include hydrocarbon oils and halo-substituted
hydrocarbon
oils such as polymerized and interpolymerized olefins (e.g., polybutylenes,
polypropylenes,
propylene-isobutylene copolymers, chlorinated polybutylenes, poly(1-hexenes),
poly(1-
octenes), poly(1-decenes)); alkylbenzenes (e.g., dodecylbenzenes,
tetradecylbenzenes,
dinonylbenzenes, di(2-ethylhexyl)benzenes); polyphenyls (e.g., biphenyls,
terphenyls>
CA 02471196 2004-06-11
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alkylated polyphenols); and alkylated diphenyl ethers and alkylated diphenyl
sulfides and
derivative, analogs and homologs thereof.
Alkylene oxide polymers and interpolymers and derivatives thereof where the
terminal hydroxyl groups have been modified by esterificati.on,
etherification, etc., constitute
another class of known synthetic lubricating oils. These are exemplified by
polyoxyalkylene
polymers prepared by polymerization of ethylene oxide or propylene oxide, and
the alkyl and
aryl ethers of polyoxyalkylene polymers (e.g., methyl-polyiso-propylene glycol
ether having a
molecular weight of 1000 or diphenyl ether of poly-ethylene glycol having a
molecular
weight of 1000 to 1500); and mono- and polycarboxylic esters thereof, for
example, the acetic
acid esters, mixed C3-C$ fatty acid esters and C13 Oxo acid d.iester of
tetraethylene glycol.
Another suitable class of synthetic lubricating oils comprises the esters of
dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids
and alkenyl succinic
acids, malefic acid, azelaic acid, suberic acid, sebasic acid, fumaric acid,
adipic acid, linoleic
acid dimer, malonic acid, alkylmalonic acids, alkenyl malonic acids) with a
variety of
alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl
alcohol, ethylene
glycol, diethylene glycol monoether, propylene glycol). Examples of such
esters include
dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl
sebacate, diisooctyl
azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl
sebacate, the 2-
ethylhexyl diester of linoleic acid dimer, and the complex ester formed by
reacting one mole
of sebacic acid with two moles of tetraethylene glycol and two moles of 2-
ethylhexanoic acid.
Esters useful as synthetic oils also include those made from CS to C12
monocarboxylic
acids and polyols and polyol esters such as neopentyl glycol,
tri~thylolpropane,
pentaerythritol, dipentaerythritol and tripentaerythritol.
Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy- or
polyaryloxysilicone oils and silicate oils comprise another useful class of
synthetic lubricants;
such oils include tetraethyl silicate, tetraisopropyl silicate, tetra-(2-
ethylhexyl)silicate, tetra-
(4-methyl-2-ethylhexyl)silicate> tetra-(p-tert-butyl-phenyl) silicate, hexa-(4-
methyl-2-
ethylhexyl)disiloxane, poly(methyl)siloxanes and poly(methylphenyl)siloxanes.
Other
synthetic lubricating oils include liquid esters of phosphorous-containing
acids (e.g., tricresyl
phosphate, trioctyl phosphate, diethyl ester of decylphosphonic acid) and
polymeric
tetrahydrofurans.
CA 02471196 2004-06-11
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The diluent oil may comprise a Group I, Group II, Group III, Group IV or Group
V oil
or blends of the aforementioned oils. The diluent oil may also comprise a
blend of a Group I
oil and one or more of Group II, Group III, Group N or Group V oil.
Preferably, from an
economic standpoint, the diluent oil is a mixture of a Group I oil and one or
more a Group II,
Group III, Group IV or Group V oil, more preferably a mixture of a Group I oil
and one or
more Group II or Group III oil.
Definitions for the oils as used herein are the same as those found in the
American
Petroleum Institute (API) publication "Engine ~il Licensing and Certification
System",
Industry Services Department, Fourteenth Edition, December 1996, Addendum 1,
December
1998. Said publication categorizes oils as follows:
a) Group I oils contain less than 90 percent saturates and/or greater than
0.03 percent
sulfur and have a viscosity index greater than or equal to 80 and less than
120 using the
test methods specified in Table 1.
b) Group II oils contain greater than or equal to 90 percent saturates and
less than or
equal to 0.03 percent sulfur and have a viscosity index greater than or equal
to 80 and
less than 120 using the test methods specified in Table 1. Although not a
separate
Group recognized by the API, Group II oils having a viscosity index greater
than about
110 are often referred to as "Group II+" oils.
c) Group III oils contain greater than or equal to 90 percent saturates and
less than or
equal to 0.03 percent sulfur and have a viscosity index greater than or equal
to 120
using the test methods specified in Table 1.
d) Group IV oils are polyalphaolefins (PAO).
e) Group V oils are all other base stocks not included in Group I, II, III, or
1V.
Table 1
Property Test Method
Saturates ASTM D2007
Viscosity Index ASTM D2270
Sulfur ~ AST1.~I D429=1
As noted supra, diluent oil useful in the practice of the invention has a CCS
at -35°C
of less than 3700 cPs, such as less than 3300 cPs, preferably less than 3000
cPs, such as less
than 2800 cPs and more preferably less than 2500 cPs, such as less than 2300
cPs.
CA 02471196 2004-06-11
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Diluent oil useful in the practice of the invention also has a kinematic
viscosity at
100°C (kvl~) of at least 3.0 cSt (centistokes), such as from about 3
cSt. to 5 cSt., especially
from about 3 cSt. to 4 cSt., such as from about 3.4 to 4 cSt. More active
polymer may be
required to provide suitable viscometrics when lower viscosity diluent oil is
used.
The diluent oil preferably has a saturate content of at least 65%, more
preferably at
least 75°k, such as at least 85%. Most preferably, the diluent oil has
a saturate content of
greater than 90%. Preferably, the diluent oil has a sulfur content of less
than 1 %, preferably
less than 0.6%, mare preferably less than 0.3%, by mass, such as 0 to 0.3% by
mass.
Preferably the volatility of the diluent oil, as measured by the Noack test
(ASTM
D5880), is less than or equal to about 40%, such as less than or equal to
about 35%,
preferably less than or equal to about 32%, such as less than or equal to
about 28%, more
preferably less than or equal to about 16%. Using a diluent oil having a
greater volatility
makes it difficult to provide a formulated lubricant having a Noack volatility
of less than or
equal to 15%. Formulated lubricants having a higher level of volatility may
display fuel
economy debits. Preferably, the viscosity index (VI) of the diluent oil is at
least 85,
preferably at least 100, most preferably from about 105 to 140.
The VI improver concentrate may also be used to provide a polymeric
lubricating oil flow improver (LOFI), also commonly referred to as pour point
depressant
(PPD). The LOFI is used to lower the minimum temperature at which the fluid
will flow or
can be poured and such additives are well known. Typical of such additives are
C8 to C,8
dialkyl fumaratelvinyl acetate copolymers, polymethacrylates and
styrene/maleic anhydride
ester copolymers.
The VI improver concentrates of the present invention can contain from about 4
to
about 50 mass %, such as from about 5 to about 25 mass %, preferably from
about 6 to about
20 mass %, such as from about 7 to about 15 mass °~ of VI improver and
from about 0 to
about 5 mass % of LOFI, with the remainder comprising diluent. At )east about
98 mass %.
preferably at least about 99.5 mass % of the VI improver concentrate consists
essentially of
VI improver, LOFI and diluent oil.
The VI improver concentrates of the present invention can be prepared by
dissolving
the VI improver polymer(s), and optional LOFI, in the diluent oil using well
known
techniques. When dissolving a solid VI improver polymer to form a concentrate,
the high
CA 02471196 2004-06-11
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viscosity of the polymer can cause poor diffusivity in the diluent oil. To
facilitate dissolution,
it is common to increase the surface are of the polymer by, for example,
pelletizing, chopping,
grinding or pulverizing the polymer. The temperature of the diluent oil can
also be increased
by heating using, for example, steam or hot oil. When the diluent temperature
is greatly
increased (such as to above 100°C), heating should be conducted under a
blanket of inert gas
(e.g., NZ or C02). The temperature of the polymer may also be raised using,
for example,
mechanical energy imparted to the polymer in an extruder or masticator. The
polymer
temperature can be raised above 150°C; the polymer temperature is
preferably raised under a
blanket of inert gas. Dissolving of the polymer may also be aided by agitating
the concentrate,
such as by stirnng or agitating (in either the reactor or in a tank), or by
using a recirculation
pump. Any two or more of the foregoing techniques can also be used in
combination.
Concentrates can also be formed by exchanging the polymerization solvent
(usually a volatile
hydrocarbon such as, for example, propane, hexane or cyclohexane) with oil.
This exchange
can be accomplished by, for example, using a distillation column to assure
that substantially
none of the polymerization solvent remains.
The concentrates of the invention are principally used in the formulation of
crankcase
lubricating oils for passenger car and heavy duty diesel engines (fully
formulated lubricants),
which fully formulated lubricants comprise a major amount of an oil of
lubricating viscosity
and a viscosity index (VI) improver as described above, in an amount effective
to meet the
requirements of the selected grade. Such fully formulated lubricants may
contain the VI
improver provided by the concentrate of the invention in an amount of from
about 0.1 mass %
to about 3 mass %, preferably from about 0.2 mass °!o to about 2 mass
%, more preferably
from about 0.3 mass % to about 1.5 mass %, stated as mass percent active
ingredient (AI)
based on the total mass of the formulated lubricant. The amount of VI
irnprover needed to
provide the fully formulated lubricant with the required viscometric
properties is further a
function of the TE of the VI improver employed.
In addition to the VI impraver and LOFI, a fully formulated lubricant can
generally
contain a number of other performance improving additives selected from
ashless dispersants,
metal-containing, or ash-forming detergents, antiwear agents, oxidation
inhibitors or
antioxidants, friction modifiers and fuel economy agents, and stabilizers or
emulsifiers.
Conventionally, when formulating a lubricant, the VI improver and/or VI
improver and LOFI,
will be provided to the formulator in one concentrated package, and
combinations of the
remaining additives will provided in one or more additional concentrated
packages,
oftentimes referred to as DI (dispersant-inhibitor) packages.
CA 02471196 2004-06-11
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Ashless dispersants maintain in suspension oil inso~lubles resulting from
oxidation of
the oil during wear or combustion. They are particularly advantageous for
preventing the
precipitation of sludge and the formation of varnish, particularly in gasoline
engines.
Metal-containing or ash-forming detergents function both as detergents to
reduce or
remove deposits and as acid neutralizers or rust inhibitors, thereby reducing
wear and
corrosion and extending engine life. Detergents generally comprise a polar
head with a long
hydrophobic tail, with the polar head comprising a metal salt of an acidic
organic compound.
The salts may contain a substantially stoichiometric amount of the metal in
which case they
are usually described as normal or neutral salts, and would typically have a
total base number
or TBN (as can be measured by ASTM D2896) of from 0 to 80. A large amount of a
metal
base may be incorporated by reacting excess metal compound (e.g., an oxide or
hydroxide)
with an acidic gas (e.g., carbon dioxide). The resulting overbased detergent
comprises
neutralized detergent as the outer layer of a metal base (e.g. carbonate)
micelle. Such
overbased detergents may have a TBN of 150 or greater, and typically will have
a TBN of
from 250 to 450 or more.
Dihydrocarbyl dithiophosphate metal salts are frequently used as antiwea~ and
antioxidant agents. The metal may be an alkali or alkaline earth metal, or
aluminum, lead, tin,
molybdenum, manganese, nickel or copper. The zinc salts are most commonly used
in
lubricating oil and may be prepared in accordance with known techniques by
first forming a
dihydrocarbyl dithiophosphoric acid (DDPA), usually by reaction of one or more
alcohol or a
phenol with PISS and then neutralizing the formed DDPA with a zinc compound.
For
example, a dithiophosphoric acid may be made by reacting mixtures of primary
arid
secondary alcohols. Alternatively, multiple dithiophosphoric acids can be
prepared where the
hydrocarbyl groups on one are entirely secondary in character and the
hydrocarbyl groups on
the others are entirely primary in character. To make the zinc salt, any basic
or neutral zinc
compound could be used but the oxides, hydroxides and carbonates are most
generally
employed. Commercial additives frequently contain an excess of zinc due to the
use of an
excess of the basic zinc compound in the neutralization reaction.
Oxidation inhibitors or antioxidants reduce the tendency of mineral oils to
deteriorate
in service. Oxidative deterioration can be evidenced by sludge in the
lubricant, varnish-like
deposits on the metal surfaces, and by viscosity growth. Such oxidation
inhibitors include
hindered phenols, alkaline earth metal salts of alkylphenolthioesters having
preferably CS to
CA 02471196 2004-06-11
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C,2 alkyl side chains, calcium nonylphenol sulfide, oil soluble phenates and
sulfurized
phenates, phosphosulfurized or sulfurized hydrocarbons, phosphorous esters,
metal
thiocarbamates, oil soluble copper compounds as described in U.S. Patent No.
4,867,890, and
molybdenum-containing compounds and aromatic amines.
Known friction modifiers include oil-soluble organo-molybdenum compounds. Such
organo-molybdenum friction modifiers also provide antioxidant and antiwear
credits to a
lubricating oil composition. As an example of such oil soluble organo-
molybdenum compounds,
there may be mentioned the dithiocarbamates, dithiophosphates,
dithiophosphinates, xanthates,
thioxanthates, sulfides, and the like, and mixtures thereof. Particularly
preferred are
molybdenum dithiocarbamates, dialkyldithiophosphates, alkyl xanthates and
alkylthioxanthates.
Other known friction modifying materials include glyceryl monoesters of higher
fatty
acids, for example, glyceryl mono-oleate; esters of Long chain polycarboxylic
acids with diols,
for example, the butane diol ester of a dimerized unsaturated fatty acid;
oxazoline
compounds; and alkoxylated alkyl-substituted mono-amines, diamines arid alkyl
ether amines,
for example, ethoxylated tallow amine and ethoxylated tallow ether amine.
Foam control can be provided by an antifoamant of the polysiloxane type, for
example, silicone oil or polydimethyl siloxane.
Some of the above-mentioned additives can provide a multiplicity of effects;
thus for
example, a single additive may act as a dispersant-oxidation inhibitor. This
approach is well
known and need not be further elaborated herein.
It may also be necessary to include an additive which maintains the stability
of the
viscosity of the blend. Thus, although polar group-containing additives
achieve a suitably
low viscosity in the pre-blending stage it has been observed. that some
compositions increase
in viscosity when stored for prolonged periods. Additives which are effective
in controlling
this viscosity increase include the long chain hydrocarbons functionalized by
reaction with
mono- or dicarboxylic acids or anhydrides which are used in the preparation of
the ashless
dispersants as hereinbefore disclosed.
Representative effective amounts of such additional additives, when used in
3S crankcase lubricants, are listed below:
CA 02471196 2004-06-11
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ADDITIVE Mass % (Broad)Mass % (Preferred)
Ashless Dis ersant 0.1 - 20 1 - 8
Metal Deter ents 0.1 - 15 0.2 - 9
Corrosion Inhibitor 0 - 5 0 - 1.5
Metal Dih drocarb 1 Dithio 0.1 - 6 0.1 - 4
hos hate
Antioxidant 0 - 5 0.01 - 2
Pour Point De ressant 0.01 - 5 0.01 - 1.5
Antifoamin A ent 0 - 5 0.001 - 0.15
Su lemental Antiwear A ents 0 - 1.0 0 - 0.5
Friction Modifier 0 - 5 0 - 1.5
Basestock Balance Balance
This invention will be further understood by reference to the following
examples. In
the following Examples, the properties of certain VI improvers are described
using certain
terms of art, defined below. AlI weight percents expressed herein (unless
otherwise
indicated) are based on active ingredient (AI) content of the additive, and/or
upon the total
weight of any additive-package, or formulation which will be the sum of the AI
weight of
each additive plus the weight of total oil and/or diluent.
"Shear Stability Index (SSI)" measures the ability of polymers used as V.I.
improvers
in crankcase lubricants to maintain thickening power during SSI is indicative
of the resistance
of a polymer to degradation under service conditions. The higher the SSI, the
less stable the
polymer, i.e., the more susceptible it is to degradation. SSI is defined as
the percentage of
polymer-derived viscosity loss and is calculated as follows:
SSI = 100 X ~'~esh after
~fre~h ~~it
wherein kvfre~, is the kinematic viscosity of the polymer-containing solution
before
degradation and kva~r is the kinematic viscosity of the polymer-containing
solution after
degradation. SSI is conventionally determined using ASTM D62?8-98 (known as
the Kurt-
2Q ~rban (KO) or D~1 bench test). Tl~e polymer under test is dissolved in
suitable: base oil (for
example, solvent extracted 150 neutral) to a relative viscosity of 2 to 3
centistokes at 100°C
and the resulting fluid is pumped through the testing apparatus specified in
the ASTM D6278-
98 protocol.
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"Thickening Efficiency (TE)" is representative of a polymers ability to
thicken oil per
unit mass and is defined as:
TE = 2 In ~°~l+polymer
c In 2 kvo~l
wherein c is polymer concentration (grams of polymer/100 grams solution),
kv°;~+polyaer is
kinematic viscosity of the polymer in the reference oil, and kv°;, is
kinematic viscosity of the
reference oil.
"Cold Cranking Simulator (CCS)" is a measure of the cold-cranking
characteristics of
crankcase lubricants and is conventionally determined using a technique
described in ASTM
D5293-92.
"Crystallinity" in ethylene-alpha-olefin polymers can be measured using X-ray
techniques known in the art as well as by the use of a differential scanning
calorimetry (DSC)
test. DSC can be used to measure crystallinity as follows: a polymer sample is
annealed at
room temperature (e.g., 20-2S°C) for at least 24 hours before the
measurement. Thereafter,
the sample is first cooled to -100°C from room temperature,. and then
heated to 150 C at
10°C/min. Crystallinity is calculated as follows:
Crystallinity = (~ OH )x xmethyle>ie ''~ 4110 X 100% ,
wherein EOH (J/g) is the sum of the heat absorbed by the polymer above its
glass transition
temperature, X~~y~ene is the molar fraction of ethylene in the polymer
calculated, e.g., from
proton NMR data, 14 (g/mol) is the molar mass of a methylene unit, and 4110
(J/mol) is the
heat of fusion for a single crystal of polyethylene at equilibrium.
EXAMPLES
Diluent oils used in the following Examples are characterized in Table 2. III
improvers used in the following Examples are characterized in Table 3, below:
CA 02471196 2004-06-11
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Table 2
Diluent Oils and DiIuent OiI Blends
Dil. Oil Type Noack kv,~ CCS @ -35C
No.
Oil I Group I 27 4.0 5926
Oil 2 Group I 19.8 5.2 18468
Oil 3 Group II 26.2 4.1 5033
Oil 4 Group II 16.9 4.3 3332
Oil 5 Group II+ 14.7 4.5 5948
Oil 6 Group III 15.4 4.2 2841
Oil 7 Group II+ blend 26.2 4.0 3317
Oil 8 Group III/Group 24.5 3.8 2136
Oil 9 II+ blend 22.4 3.6 1038
Group II+ blend
Oil 10 Group a+/Group I 27.6 3.5 1486
Oil 11 blend 92.8 3.1 1840
Oil 12 Group I 20.8 3.5 1854
Group UGroup III
blend
Table 3
S VIImprovers
VI Improver Type Ethylene Content*Mn Mn/MW SST
No.
VII 1 Amorphous OCP 49.4 mass % 55,000 2.0 35
VII 2 Amorphous OCP 49.4 mass % 97,500 2.0 50
*mass % of polymer derived from ethylene monomer, based on total mass of
polymer
Example 1
Concentrates containing 9 mass % of polymer were prepaxed from the above
diluent
IO oils and VI improver polymers, and used in combination with a common DI
package to
formulate lubricants of varying grades using the indicated base stock oils.
The formulated
lubricants were of the type suitable for use as either a passenger car motor
oil (PCMO) or
heavy duty diesel (HDD) crankcase lubricant and had a Noack volatility below
1S%. The
CCS properties of the fully formulated lubricants w~.re deternunetc and the
results provi~ed.
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Table 4
VII Dil. SW30 PCMO 1OW40 PCMO 10W30 PCMO
Oil
No. No. Group TI+ BasestockGroup I/II BasestockGroup I Basestock
Blend
CCS @ -30C (cP)CCS C~ -25C (cP) CCS C~ -25C
(cP)
1 1 5685 7129 6564
1 5 5699 6872 ----
1 7 5514 6578 ----
__ - ____ 6179
As shown, for each of the noted grades, the formulated lubricant prepared
using the
concentrate containing a diluent oil of the invention (Oil. Nos. 7 and 8)
provided improved
CCS performance using an amorphous OCP VI improver.
Example 2
Concentrates containing 9 mass °~o of VII polymer 1 were prepared from
the above
diluent oils and used, in combination with a common DI package and a base
stock blend of
Group I and Group II base stock oil, to formulate 1OW30 grade HDD crankcase
lubricants.
The CCS, Noack volatility and kinematic viscosities of the fully formulated
lubricants were
determined and the results provided.
Table 5
Dil. Oil CCS C -2SC (cP)Predicted Noack (mass kv,~
No. %)
1 6292 15.9 10.72
6 6033 15.5 10.78
In the noted formulations, the concentrate containing the claimed diluent oil
(Oil 6)
provided improved CCS with an amorphous OCP VI improver, with comparable Noack
volatility and kinematic viscosity characteristics.
Example 3
Concentrates containing 9 mass % of VII polymer 1 were prepared using the
above
diluent oils and used, in combination with a common DI package arid a Group
II+ base stock
oil, to formulate 5W30 grade PCMO crankcase lubricants. The amount of VI
improver
concentrate was adjusted such that the formulated lubricants all had a Noack
volatility no
greater than 15 %. The CCS, and kinematic viscosities of the fully formulated
lubricants
were determined and the results provided.
CA 02471196 2004-06-11
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Table 6
Dil. Oil CCS @ -25C (cP)Predicted Noack (masskv,~
No. %)
~
1 6193 15.0 10.63
7 6032 14.8 10.47
6 5826 15.0 10.61
6 5931 14.5 10.67
In the noted formulations, the concentrate containing the claimed diluent oils
(Oils 6
and 7) provided improved CCS with an amorphous OCP VI improver, ae comparable
Noack
volatility and with similar kinematic viscosity characteristics.
Example 4
Concentrates containing 9 mass % of VII polymer 1 were prepared from the above
diluent oils and used in combination with a DI package and a Group I base
stock oil, to
formulate 10W30 grade PCMO crankcase lubricants. The CCS, and kinematic
viscosities of
the fully formulated lubricants were determined and the results provided.
Table 7
Dil. Oil CCS @ -25C Predicted Noack (masskv,~
No. (cP) %)
~
1 6554 15.5 10.53
6 6268 15.0 10.50
11 6198 21.5 10.32
8 6179 15.5 10.43
In the noted formulations, the concentrate containing the claimed diluent oils
(Oils 6,
8 and 11) provided improved CCS with an amorphous OCP VI improver and similar
kinematic viscosity characteristics. However, as the results further show,
when using a
diluent oil having a Noack viscosity above 40 % (Dil. Oil I 1), it rnay not be
possible to blend
a formulated oil within the desired grade having an acceptable NoaGh
volatility.
A description of a composition comprising, consisting of, or consisting
essentially of multiple specified components, as presented herein and in the
appended claims, should be construed to also encompass compositions
made by admixing said multiple specified components. The
CA 02471196 2004-06-11
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principles, preferred embodiments and modes of operation of the present
invention have been
described in the foregoing specification. What applicants submit is their
invention, however,
is not to be construed as limited to the particular embodiments disclosed,
since the disclosed
embodiments are regarded as illustrative rather than limiting. Changes may be
made by those
skilled in the art without departing from the spirit of the invention.
